Sorry if that response was no help to you, but I just couldn't resist.
Anyway..
Have you tried installing updated drivers from ATI? (ATI... new drivers? *snicker*) Sorry...
If you're already using new drivers, possibly even an older version?
Also, if that doesnt work... what motherboard/chipset do you have the card hooked up to? I might have some suggestions depending on the rest of your system.